Application of Antai high-precision voltage source in semiconductor laser testing

Semiconductor lasers are core components in the fields of optical fiber communication, laser display, gas detection, etc., and have attracted extensive attention from scientific and technological personnel around the world. In the production and development of semiconductor lasers, the measurement of the optoelectronic characteristics of lasers is particularly important, and is a key link in controlling the stability of the laser preparation process and the reliability of laser performance.

Semiconductor lasers are semiconductor photoelectric conversion devices. As shown in Figure 1, semiconductor lasers are composed of multiple layers of materials. From bottom to top, they include back electrode, substrate, lower light confinement layer, lower waveguide layer, active layer, upper waveguide layer, upper confinement layer, and upper electrode. Different layers are composed of different epitaxial materials. Such a layered structure is intended to achieve (1) carrier (electron, hole) injection and recombination luminescence, and (2) lateral confinement of photons to form an optical waveguide. The epitaxial layered structure must undergo an etching process to form a ridge waveguide, and a contact electrode is prepared on the ridge waveguide.

The purpose of the ridge waveguide is: (1) to limit the lateral diffusion of current, and (2) to form a lateral waveguide for photons. The prepared wafer is subjected to cleavage, coating, welding, wire bonding and other processes to obtain the laser to be measured, as shown in Figure 2. When current is injected into the laser electrode, a large number of electrons and holes on both sides of the laser PN junction flow into the active area, where electron-hole pairs recombine to generate a large number of photons. The photons propagate along the axis under the action of the waveguide. At the end face of the laser, the reflected light forms the lasing condition, and the transmitted light is the laser output by the laser.

The operating characteristics of a laser are mainly reflected in (1) PN junction characteristics, series resistance, (2) laser lasing threshold, and laser slope efficiency. These characteristics determine the laser's optical power, power conversion efficiency, operating life, and other properties. PIV measurement methods are often used in production and scientific research to obtain these important parameters.

The ATS-2000V series is a voltage source with high precision and high stability voltage output. The maximum output voltage is 200V, the minimum voltage resolution can reach 2μV, the output accuracy is high, and the noise is low. The operation panel LCD display is simple, easy to understand and easy to operate. The system has a simple structure, high precision, good reliability and fast speed. While improving production efficiency, it also increases test accuracy and reliability, and reduces the cost of a large number of tests. The integrated PIV system is mainly composed of the ATS-2000V dual-channel precision source measurement unit SMU, integrating sphere, fixture and software. One channel of the ATS-2000V is used as the current source of the laser and measures the voltage V of the laser at the same time. The laser light of the LD is coupled into the integrating sphere, and is converted into photocurrent by the integrating sphere detector and enters another channel of the ATS-2000V high-precision voltage source. The photocurrent measured by the ATS-2000V is multiplied by the power-to-current conversion coefficient of the integrating sphere detector to obtain the output power of the laser. The B2900A is connected to the PIV measurement software via the USB port to complete measurement control and data acquisition.

The scalability of the integrated PIV system is also an outstanding advantage in its application in the field of semiconductor laser research and development. The hardware part of the integrated PIV system includes the ATS-2000V precision measurement unit and the measurement platform, which are connected to the computer via ports such as GPIB or USB. Therefore, the hardware part of the integrated PIV system can cooperate with the test software program written by the user through software platforms such as National Instrument to complete the more complex measurement tasks required by the user.

In the production and development of semiconductor lasers, a large number of PIV tests are required for semiconductor laser chips. Compared with the traditional discrete and complex PIV test system, the PIV test system integrated with the ATS-2000V precision measurement unit has the advantages of simple system structure, convenient operation, high accuracy, strong reliability, and rapid measurement, which greatly reduces the operating cost and time cost of PIV performance measurement of laser chips, and increases the flexibility of PIV measurement. The ATS-2000V high-precision voltage source will be widely used in the fields of semiconductor laser production and scientific research.